Method and apparatus for enhanced lifetime and performance of ion source in an ion implantation system

ABSTRACT

An ion implantation system and process, in which the performance and lifetime of the ion source of the ion implantation system are enhanced, by utilizing isotopically enriched dopant materials, or by utilizing dopant materials with supplemental gas(es) effective to provide such enhancement.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International ApplicationPCT/US2011/026388, with an international filing date of Feb. 26, 2011 inthe names of Robert Kaim, et al. for “METHOD AND APPARATUS FOR ENHANCEDLIFETIME AND PERFORMANCE OF ION SOURCE IN AN ION IMPLANTATION SYSTEM,”which International Application claims the benefit of priority under 35USC 119 of U.S. Provisional Patent Application No. 61/308,428 filed Feb.26, 2010 in the names of Robert Kaim, et al. for “METHOD AND APPARATUSFOR ENHANCED LIFETIME AND PERFORMANCE OF ION SOURCE IN AN IONIMPLANTATION SYSTEM” and U.S. Provisional Patent Application No.61/390,715 filed Oct. 7, 2010 in the names of Robert Kaim, et al. for“METHOD AND APPARATUS FOR ENHANCED LIFETIME AND PERFORMANCE OF IONSOURCE IN AN ION IMPLANTATION SYSTEM.” The disclosures of saidInternational Application and said U.S. Provisional Patent ApplicationNos. 61/308,428 and 61/390,715 are hereby incorporated herein byreference, in their respective entireties, for all purposes.

FIELD

The present disclosure relates to ion implantation using dopants anddopant gas mixtures for enhanced lifetime and performance of an ionsource in an ion implantation system.

BACKGROUND

Ion implantation as practiced in semiconductor manufacturing involvesdeposition of a chemical species into a substrate, such as amicroelectronic device wafer, by impingement of energetic ions of suchspecies on the substrate. In order to generate the ionic implantationspecies, the dopant gas, which may for example comprise a halide orhydride of the dopant species, is subjected to ionization. Thisionization is carried out using an ion source to generate an ion beam.

Once generated at the ion source, the ion beam is processed byextraction, magnetic filtering, acceleration/deceleration, analyzermagnet processing, collimation, scanning and magnetic correction toproduce the final ion beam that is impinged on the substrate.

Various types of ion sources have been developed, including inductivelyheated cathode ion sources, Freeman, Bernas, and various others, butregardless of the specific type of ion source employed, the ion sourcemust be capable of continuous operation for extended periods of time,without the occurrence of “glitching” or other impairment that wouldnecessitate shut-down, maintenance or repair of the ion source.Accordingly, ion source lifetime is a critical characteristic of the ionimplantation system, as regards the efficient and cost-effectiveoperation of the system.

Ion source failures are attributable to various causes, includingaccumulation of deposits on cathode surfaces that negatively affectthermionic emission of ions, resulting in lowered arc currents, reducedperformance and shortened lifetime of the ion source, as well asdeleterious etching reactions from such dopant gases as germaniumtetrafluoride as a result of the generation of free fluorine in the arcchamber, as well as stripping or sputtering of cathode materialresulting in loss of physical integrity of the cathode and consequentreduction of performance and lifetime of the ion source.

In consequence of the need to avoid ion source failures, and to maintainthe operating efficiency and lifetime of the ion source at high levels,the art is continually engaged in efforts to enhance lifetime andperformance of ion sources in ion implantation systems.

SUMMARY

The present disclosure relates to ion implantation systems andprocesses, and to method and apparatus for achieving enhanced lifetimeand performance of ion sources in such systems and processes.

In one aspect, the disclosure relates to an ion implantation process,comprising flowing a dopant composition to an ion source for generationof ionic dopant species for implantation, wherein the dopant compositionis selected from the group consisting of:

-   (i) germanium compounds isotopically enriched to above natural    abundance level of at least one germanium isotope of mass 70, 72,    73, 74 or 76, wherein the isotopically enriched level of said at    least one germanium isotope is greater than 21.2% for mass 70    germanium isotope, greater than 27.3% for mass 72 germanium isotope,    greater than 7.9% for mass 73 germanium isotope, greater than 37.1%    for mass 74 germanium isotope, and greater than 7.4% for mass 76    germanium isotope, with the proviso that when the dopant composition    consists of germanium tetrafluoride isotopically enriched in mass 72    germanium isotope, said isotopically enriched level is greater than    51.6% for the mass 72 germanium isotope; and-   (ii) dopant gas formulations comprising a dopant gas and a    supplemental gas, wherein the supplemental gas includes at least one    of a diluent gas and a co-species gas, and wherein at least one of    the dopant gas and, when present, a co-species gas, is isotopically    enriched.

In another aspect, the disclosure relates to a method of operating anion source in an ion implantation process of the type described above,comprising: sequentially flowing to the ion source different dopantmaterials comprised in said dopant composition;

-   monitoring cathode bias power during operation of the ion source    during the sequential flow of said different dopant materials to the    ion source; and-   in response to the monitored cathode bias power, modulating at least    one of said sequentially supplied dopant compositions, to extend    operating lifetime of the ion source, cathode and/or one or more    other components of the ion source.

A further aspect of the disclosure relates to a method of improvingperformance and lifetime of an ion source arranged to generate ionicdoping species for ion implantation from a dopant feedstock, comprisinggenerating said ionic doping species from a dopant composition asdescribed above in connection with the ion implantation process of thedisclosure.

The disclosure relates in another aspect to an ion implantation system,comprising an ion source and a dopant composition source arranged forsupplying dopant composition to said ion source, wherein said dopantcomposition source comprises a dopant composition as described above inconnection with the ion implantation process of the disclosure.

Another aspect of the disclosure relates to a dopant feedstockapparatus, comprising a vessel having interior volume, and a dopantfeedstock in the interior volume, wherein the dopant feedstock comprisesa dopant composition as described above in connection with the ionimplantation process of the disclosure.

A further aspect of the disclosure relates to a method of increasing atleast one of source life and turbo pump life in an ion implantationsystem in which germanium ions are implanted in a substrate, said methodcomprising ionizing a germanium-containing dopant gas in an ionizationchamber of said ion implantation system, wherein saidgermanium-containing dopant gas comprises a mixture of germane and oneor more of hydrogen, argon, nitrogen, and helium, wherein said dopantgas optionally is isotopically enriched in at least one isotopic Gespecies

Yet another aspect of the disclosure relates to a method of increasingion source life in an ion implantation system wherein germaniumtetrafluoride is introduced and ionized in said ion source, said methodcomprising introducing ammonia with said germanium tetrafluoride to theion source, and wherein said germanium tetrafluoride optionally isisotopically enriched in at least one Ge isotopic species.

A further aspect of the disclosure relates to a dopant gas compositioncomprising a dopant gas and a supplemental gas, wherein the supplementalgas includes at least one of a diluent gas and a co-species gas, andwherein at least one of the dopant gas and, when present, a co-speciesgas, is isotopically enriched.

In another aspect, the disclosure relates to a method of operating anion source, comprising:

-   sequentially flowing different dopant materials to the ion source;-   monitoring cathode bias power during operation of the ion source    during the sequential flow of said different dopant materials to the    ion source; and-   in response to the monitored cathode bias power, modulating at least    one of said sequentially supplied dopant compositions, to extend    operating lifetime of the ion source, cathode and/or one or more    other components of the ion source.

A still further aspect of the disclosure relates to a method ofoperating an ion source, comprising:

-   flowing dopant material to the ion source;-   monitoring cathode bias power during operation of the ion source    during the flow of said dopant material to the ion source; and-   in response to the monitored cathode bias power, flowing a cleaning    or deposition agent to the ion source, to extend operating lifetime    of the ion source, cathode and/or one or more other components of    the ion source, in relation to a corresponding ion source lacking    said flowing a cleaning or deposition agent thereto.

Other aspects, features and embodiments of the disclosure will be morefully apparent from the ensuing description and appended claims.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic representation of an ion implant process systemaccording to one aspect of the disclosure.

FIG. 2 is a schematic representation of an ion implant process systemaccording to another aspect of the disclosure.

DETAILED DESCRIPTION

The present disclosure relates to the use of isotopically enricheddopant and/or supplemental materials for improving the lifetime (servicelife) and performance of an ion source of an ion implantation system.

As used herein, the singular forms “a”, “and”, and “the” include pluralreferents unless the context clearly dictates otherwise.

The disclosure, as variously set out herein in respect of features,aspects and embodiments thereof, may in particular implementations beconstituted as comprising, consisting, or consisting essentially of,some or all of such features, aspects and embodiments, as well aselements and components thereof being aggregated to constitute variousfurther implementations of the invention. The disclosure is set outherein in various embodiments, and with reference to various featuresand aspects of the invention. The disclosure contemplates such features,aspects and embodiments in various permutations and combinations, asbeing within the scope of the disclosure. The disclosure may thereforebe specified as comprising, consisting or consisting essentially of, anyof such combinations and permutations of these specific features,aspects and embodiments, or a selected one or ones thereof.

The compounds, compositions, features, steps and methods of thedisclosure may be further specified in particular embodiments byprovisos or limitations excluding specific substituents, isotopes,moieties, structures, ingredients, characteristics, steps or conditions,as applicable, in relation to various specifications andexemplifications thereof set forth herein.

The ion implantation systems and processes of the present disclosure asa result of using such isotopically enriched dopant and/or supplementalmaterials achieve enhanced ion source lifetime and performance, inrelation to corresponding ion implantation systems and processes notusing such isotopically enriched dopant and/or supplemental materials.

As used herein, the term “dopant gas” refers to a gas-phase materialincluding a dopant species, i.e., the species to be implanted in the ionimplantation substrate, as coordinated or associated to a non-dopantcomponent, such as a hydride, halide, organo or other moiety. Examplesof dopant gases include germanium tetrafluoride, germane, borontrifluoride, diborane, silicon tetrafluoride, silane, phosphine andarsine.

The term “supplemental gas” as used herein refers to a diluent gas or aco-species gas.

A diluent gas is a gas that does not contain the dopant species and iseffective in mixture with the dopant gas to improve the lifetime andperformance of an ion source processing such diluent gas-containingmixture with the dopant gas, as compared to the lifetime and performanceof a corresponding ion source processing the dopant gas without thepresence of the diluent gas. Examples of illustrative diluent gasesinclude hydrogen, argon, fluorine, and xenon.

A co-species gas is a gas that contains the same dopant species as thedopant gas, wherein such same dopant species is coordinated orassociated to a non-dopant component that is different from thenon-dopant component of the dopant gas.

For example, the dopant gas may be germanium tetrafluoride, and theco-species gas may be germane, GeH₄.

The disclosure in one aspect relates to an ion implantation process,comprising flowing a dopant composition to an ion source for generationof ionic dopant species for implantation, wherein the dopant compositionis selected from the group consisting of:

-   (i) germanium compounds isotopically enriched to above natural    abundance level of at least one germanium isotope of mass 70, 72,    73, 74 or 76, wherein the isotopically enriched level of said at    least one germanium isotope is greater than 21.2% for mass 70    germanium isotope, greater than 27.3% for mass 72 germanium isotope,    greater than 7.9% for mass 73 germanium isotope, greater than 37.1%    for mass 74 germanium isotope, and greater than 7.4% for mass 76    germanium isotope, with the proviso that when the dopant composition    consists of germanium tetrafluoride isotopically enriched in mass 72    germanium isotope, said isotopically enriched level is greater than    51.6% for the mass 72 germanium isotope; and-   (ii) dopant gas formulations comprising a dopant gas and a    supplemental gas, wherein the supplemental gas includes at least one    of a diluent gas and a co-species gas, and wherein at least one of    the dopant gas and, when present, a co-species gas, is isotopically    enriched.

In various embodiments of such process, the dopant composition can beselected from the group consisting of germanium compounds isotopicallyenriched to above natural abundance level of at least one germaniumisotope of mass 70, 72, 73, 74 or 76. The dopant composition cantherefore comprise: a germanium compound isotopically enriched togreater than 21.2% in mass 70 germanium isotope; a germanium compoundisotopically enriched to greater than 27.3% in mass 72 germaniumisotope; a germanium compound isotopically enriched to greater than51.6% in mass 72 germanium isotope; a germanium compound isotopicallyenriched to greater than 7.9% in mass 73 germanium isotope; a germaniumcompound isotopically enriched to greater than 37.1% in mass 74germanium isotope; or a germanium compound isotopically enriched togreater than 7.4% in mass 76 germanium isotope.

The process in other embodiments may be practiced with the germaniumcompound comprising at least one of germanium tetrafluoride and germane.For example, the germanium compound may comprise germaniumtetrafluoride, in which germanium in the germanium tetrafluoride canhave: an isotopically enriched level of mass 70 germanium isotope thatis greater than 21.2%; an isotopically enriched level of mass 72germanium isotope that is greater than 27.3%; an isotopically enrichedlevel of mass 72 germanium isotope that is greater than 51.6%; anisotopically enriched level of mass 73 germanium isotope that is greaterthan 7.9%; an isotopically enriched level of mass 74 germanium isotopethat is greater than 37.1%; or an isotopically enriched level of mass 76germanium isotope that is greater than 7.4%.

Still other embodiments of the disclosure can be carried out in whichthe dopant composition comprises germane, and the germanium in thegermane has: an isotopically enriched level of mass 70 germanium isotopethat is greater than 21.2%; an isotopically enriched level of mass 72germanium isotope that is greater than 51.6%; an isotopically enrichedlevel of mass 73 germanium isotope that is greater than 7.9%; anisotopically enriched level of mass 74 germanium isotope that is greaterthan 37.1%; or an isotopically enriched level of mass 76 germaniumisotope that is greater than 7.4%.

The ion implantation process broadly described above can be carried outin other embodiments in which the dopant composition is selected fromthe group consisting of dopant gas formulations comprising a dopant gasand a supplemental gas, wherein the supplemental gas includes at leastone of a diluent gas and a co-species gas, and wherein at least one ofthe dopant gas and, when present, a co-species gas, is isotopicallyenriched. In various embodiments, such at least one of the dopant gasand, when present, the co-species gas, that is isotopically enriched,can be selected from the group consisting of germanium compoundsisotopically enriched above natural abundance level of at least onegermanium isotope of mass 70, 72, 73, 74 or 76. Illustrative examples ofsuch isotopically enriched germanium compounds include: germaniumcompounds isotopically enriched to greater than 21.2% in mass 70germanium isotope; germanium compounds isotopically enriched to greaterthan 27.3% in mass 72 germanium isotope; germanium compoundsisotopically enriched to greater than 51.6% in mass 72 germaniumisotope; germanium compounds isotopically enriched to greater than 7.9%in mass 73 germanium isotope; germanium compounds isotopically enrichedto greater than 37.1% in mass 74 germanium isotope; and germaniumcompounds isotopically enriched to greater than 7.4% in mass 76germanium isotope.

In various implementations of the ion implantation process, the dopantcomposition can comprise at least one of germanium tetrafluoride andgermane. For example, the dopant composition can comprise germaniumtetrafluoride, in which the germanium has: an isotopically enrichedlevel of mass 70 germanium isotope that is greater than 21.2%; anisotopically enriched level of mass 72 germanium isotope that is greaterthan 27.3%; an isotopically enriched level of mass 72 germanium isotopethat is greater than 51.6%; an isotopically enriched level of mass 73germanium isotope that is greater than 7.9%; an isotopically enrichedlevel of mass 74 germanium isotope that is greater than 37.1%; or anisotopically enriched level of mass 76 germanium isotope that is greaterthan 7.4%.

Alternatively, the dopant composition can comprise germane, in which thegermanium has: an isotopically enriched level of mass 70 germaniumisotope that is greater than 21.2%; an isotopically enriched level ofmass 72 germanium isotope that is greater than 27.3%; an isotopicallyenriched level of mass 73 germanium isotope that is greater than 7.9%;an isotopically enriched level of mass 74 germanium isotope that isgreater than 37.1%; or an isotopically enriched level of mass 76germanium isotope that is greater than 7.4%.

In other embodiments of the process, the supplemental gas may include adiluent gas, e.g., at least one gas species selected from the groupconsisting of argon, hydrogen, fluorine and xenon. Still otherembodiments may include a supplemental gas comprising a co-species gas.

Yet other embodiments of the process employ a dopant compositioncomprising at least one of germanium tetrafluoride, germane, borontrifluoride, diborane, silicon tetrafluoride and silane.

Still other embodiments of the process employ a dopant gas selected fromthe group consisting of germanium tetrafluoride, germane, borontrifluoride, diborane, silicon tetrafluoride and silane, and a diluentgas comprising at least one diluent gas species selected from the groupconsisting of argon, hydrogen, fluorine, and xenon.

The dopant composition in other embodiments of the process includes adopant gas formulation selected from the group consisting of:

-   (i) isotopically enriched germanium tetrafluoride with xenon and    hydrogen;-   (ii) isotopically enriched germanium tetrafluoride with germane;-   (iii) isotopically enriched germanium tetrafluoride and isotopically    enriched germane;-   (iv) isotopically enriched boron trifluoride with xenon and    hydrogen;-   (v) isotopically enriched boron trifluoride with diborane; and-   (vi) isotopically enriched boron trifluoride and isotopically    enriched diborane.

In various embodiments of the process, the dopant gas and co-species gasare flowed in mixture with one another to the ion source for generationof ionic dopant species for implantation. Other embodiments of theprocess are carried out in which the dopant gas and co-species gas aresequentially flowed to the ion source for generation of ionic dopantspecies for implantation.

In the ion implantation process of the disclosure, the ion source in oneembodiment can be operated according to the following methodology:flowing sequentially to the ion source different dopant materialscomprised in said dopant composition different dopant materialscomprised in the dopant composition; monitoring cathode bias powerduring operation of the ion source during the sequential flow of thedifferent dopant materials to the ion source; and in response to themonitored cathode bias power, modulating at least one of thesequentially supplied dopant compositions, to extend operating lifetimeof the ion source, cathode and/or one or more other components of theion source.

The disclosure in another aspect relates to a method of improvingperformance and lifetime of an ion source arranged to generate ionicdoping species for ion implantation from a dopant feedstock, comprisinggenerating such ionic doping species from any of the dopant compositionsof the present disclosure, as variously described herein. In oneembodiment of such method, a dopant gas and co-species gas are flowed inmixture with one another to the ion source for generation of ionicdopant species for implantation. In another embodiment of such method, adopant gas and co-species gas are sequentially flowed to the ion sourcefor generation of ionic dopant species for implantation.

A further aspect of the disclosure relates to an ion implantationsystem, comprising an ion source and a dopant composition sourcearranged for supplying dopant composition to said ion source, whereinthe dopant composition source comprises any of the dopant compositionsas variously described herein. In such ion implantation system, thedopant composition may comprise dopant gas and co-species gas, and thedopant composition source may be arranged to flow the dopant gas andco-species gas in mixture with one another to said ion source forsupplying dopant composition thereto. Alternatively, the dopantcomposition source may be arranged for sequentially flowing dopant gasand co-species gas to the ion source for supply of dopant compositionthereto.

A still further aspect of the disclosure relates to a dopant feedstockapparatus, comprising a vessel having interior volume, and a dopantfeedstock in the interior volume, wherein the dopant feedstock comprisesany of the dopant compositions as variously described herein.

The disclosure relates in another aspect to a method of increasing atleast one of source life and turbo pump life in an ion implantationsystem in which germanium ions are implanted in a substrate. The methodcomprises ionizing a germanium-containing dopant gas in an ionizationchamber of the ion implantation system, wherein the germanium-containingdopant gas comprises a mixture of germane and one or more of hydrogen,argon, nitrogen, and helium, wherein the dopant gas optionally isisotopically enriched in at least one isotopic Ge species.

For example, germane may be present in such mixture at a concentrationin a range of from 5 to 35 percent volume, based on the total volume ofthe mixture.

The disclosure in a further aspect relates to a method of increasing ionsource life in an ion implantation system wherein germaniumtetrafluoride is introduced and ionized in the ion source. The methodcomprises introducing ammonia with the germanium tetrafluoride to theion source, and wherein the germanium tetrafluoride optionally isisotopically enriched in at least one Ge isotopic species. In suchmethod, the ammonia and germanium tetrafluoride may be provided in amixture in a supply vessel from which the mixture is dispensed forintroduction thereof to the ion source. Alternatively, in such method,the ammonia and germanium tetrafluoride may be provided in separatesupply vessels from which they are dispensed for introduction thereof tothe ion source. As a still further embodiment, the ammonia and germaniumtetrafluoride may be mixed with one another in the ion source afterintroduction thereof to the ion source.

Another variant of such method involves introducing xenon to the ionsource. The xenon may be introduced in mixture with ammonia and/orgermanium tetrafluoride.

In another embodiment of such method as broadly described above, thegermanium tetrafluoride may be isotopically enriched in at least one Geisotopic species, e.g., at least one Ge isotopic species comprisesgermanium isotope selected from the group consisting of ⁷⁰Ge, ⁷²Ge and⁷⁴Ge.

A further aspect of the disclosure relates to a dopant gas compositioncomprising a dopant gas and a supplemental gas, wherein the supplementalgas includes at least one of a diluent gas and a co-species gas, andwherein at least one of the dopant gas and, when present, a co-speciesgas, is isotopically enriched. The composition, wherein at least one ofthe dopant gas and, when present, the co-species gas, is isotopicallyenriched, may be selected from the group consisting of germaniumcompounds isotopically enriched above natural abundance level of atleast one germanium isotope of mass 70, 72, 73, 74 or 76.

Such compounds may include: a germanium compound isotopically enrichedto greater than 21.2% in mass 70 germanium isotope; a germanium compoundisotopically enriched to greater than 27.3% in mass 72 germaniumisotope; a germanium compound isotopically enriched to greater than51.6% in mass 72 germanium isotope; a germanium compound isotopicallyenriched to greater than 7.9% in mass 73 germanium isotope; a germaniumcompound isotopically enriched to greater than 37.1% in mass 74germanium isotope; or a germanium compound isotopically enriched togreater than 7.4% in mass 76 germanium isotope.

The dopant composition in another embodiment comprises at least one ofgermanium tetrafluoride and germane.

When the composition comprises germanium tetrafluoride, the germanium inthe germanium tetrafluoride may have: an isotopically enriched level ofmass 70 germanium isotope that is greater than 21.2%; an isotopicallyenriched level of mass 72 germanium isotope that is greater than 27.3%;an isotopically enriched level of mass 72 germanium isotope that isgreater than 51.6%; an isotopically enriched level of mass 73 germaniumisotope that is greater than 7.9%; an isotopically enriched level ofmass 74 germanium isotope that is greater than 37.1%; or an isotopicallyenriched level of mass 76 germanium isotope that is greater than 7.4%.

When the composition comprises germane, the germanium in the germane mayhave: an isotopically enriched level of mass 70 germanium isotope thatis greater than 21.2%; an isotopically enriched level of mass 72germanium isotope that is greater than 27.3%; an isotopically enrichedlevel of mass 73 germanium isotope that is greater than 7.9%; anisotopically enriched level of mass 74 germanium isotope that is greaterthan 37.1%; or an isotopically enriched level of mass 76 germaniumisotope that is greater than 7.4%.

The dopant composition in other embodiments may be constituted toinclude a supplemental gas that comprises a co-species gas, oralternatively a diluent gas, or alternatively, both a co-species gas anda diluent gas. The diluent gas can include, for example, at least onegas species selected from the group consisting of argon, hydrogen,fluorine and xenon.

The dopant composition in another embodiment can comprise at least oneof germanium tetrafluoride, germane, boron trifluoride, diborane,silicon tetrafluoride and silane. A further dopant composition caninclude dopant gas selected from the group consisting of germaniumtetrafluoride, germane, boron trifluoride, diborane, silicontetrafluoride and silane, and diluent gas comprising at least onediluent gas species selected from the group consisting of argon,hydrogen, fluorine, and xenon.

The dopant composition in specific embodiments may comprise any of:

-   (i) isotopically enriched germanium tetrafluoride with xenon and    hydrogen;-   (ii) isotopically enriched germanium tetrafluoride with germane;-   (iii) isotopically enriched germanium tetrafluoride and isotopically    enriched germane;-   (iv) isotopically enriched boron trifluoride with xenon and    hydrogen;-   (v) isotopically enriched boron trifluoride with diborane; and-   (vi) isotopically enriched boron trifluoride and isotopically    enriched diborane.

Dopant compositions of the disclosure are effective to improve thelifetime and performance of an implantation process, as compared to thelifetime and performance of a corresponding process that does notutilize isotopically enriched dopant gas and isotopically enrichedsupplemental gas.

As used herein, the term “isotopically enriched” or “enriched” inreference to a dopant gas and/or co-species gas means that the dopantspecies in such gas(es) are varied from a naturally occurring isotopicdistribution of the dopant species. By way of example, a naturalabundance isotopic distribution of concentrations of germanium in agermanium tetrafluoride dopant gas, and the isotopic distribution ofgermanium concentrations in an illustrative isotopically enrichedgermanium tetrafluoride dopant gas, are shown in the following Table I.

TABLE I Isotopic Distributions in Natural and Isotopically EnrichedGermanium Tetrafluoride Concentration (+/−1%) Isotope Natural Enriched70 21.2% 15.8% 72 27.3% 51.6% 73  7.9%  9.4% 74 37.1% 20.1% 76  7.4% 3.1%

The information shown in Table I shows that germanium isotopes occur atmass 70, 72, 73, 74 and 76, with ⁷⁴Ge being the most abundant.

The present disclosure contemplates ion implantation, wherein any one ormore of such stable isotopes of germanium is enriched, i.e., increasedin concentration above natural abundance level thereof, in the germaniumdopant gas. Thus, the dopant gas in one embodiment may comprisegermanium tetrafluoride, or germane, in which the germanium isisotopically enriched above natural abundance levels in at least oneisotope. The disclosure in another embodiment relates to germaniumdopant gases in which the dopant gas is germanium tetrafluoride, andsuch dopant gas is enriched above natural abundance level in germaniumisotope of mass 70, 72, 73 or 74, with the proviso in variousembodiments that when the germanium isotope enriched above naturalabundance level is ⁷²Ge, e.g., in germanium tetrafluoride, then theenriched concentration is greater than 51.6%, e.g., with a concentrationof ⁷²Ge that is greater than 52%, 55%, 60%, 70%, 80%, 90%, 99% or99.99%, in corresponding embodiments. In other embodiments, the enrichedlevel of ⁷²Ge in a germanium compound in the dopant composition may begreater than 27.3%.

By way of specific examples, the isotopically enriched dopant gas cancomprise a dopant selected from the group consisting of:

-   (i) germane (GeH₄), isotopically enriched in ⁷⁰Ge above 21.2%, e.g.,    with a concentration of ⁷⁰Ge that is greater than 22%, 25%, 30%,    40%, 50%, 60%, 70%, 80%, 90%, 99% or 99.99%, in various    corresponding embodiments;-   (ii) germane (GeH₄), isotopically enriched in ⁷²Ge above 27.3%,    e.g., with a concentration of ⁷²Ge that is greater than 28%, 30%,    40%, 50%, 60%, 70%, 80%, 90%, 99% or 99.99%, in various    corresponding embodiments;-   (iii) germane (GeH₄), isotopically enriched in ⁷⁴Ge above 37.1%,    e.g., with a concentration of ⁷⁴Ge that is greater than 38%, 40%,    50%, 60%, 70%, 80%, 90%, 99% or 99.99%, in various corresponding    embodiments;-   (iv) germanium tetrafluoride (GeF₄), isotopically enriched in ⁷⁰Ge    above 21.2%, e.g., with a concentration of ⁷⁰Ge that is greater than    22%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99% or 99.99%, in    various corresponding embodiments;-   (v) germanium tetrafluoride (GeF₄), isotopically enriched in ⁷²Ge    above 27.3% in some embodiments, and above 51.6% in other    embodiments, e.g., with a concentration of ⁷⁰Ge that is greater than    52%, 55%, 60%, 70%, 80%, 90%, 99% or 99.99%, in various    corresponding embodiments; and-   (i) germanium tetrafluoride (GeF₄), isotopically enriched in ⁷⁴Ge    above 37.1%, e.g., with a concentration of ⁷⁰Ge that is greater than    38%, 40%, 50%, 60%, 70%, 80%, 90%, 99% or 99.99%, in various    corresponding embodiments.

Considering usage of germanium dopants containing ⁷⁴Ge, the use of ⁷⁴Geas an implanted germanium species, or the presence thereof in a dopantcomposition carries the risk of cross contamination when such⁷⁴Ge-containing dopant is used in an implanter that also processesarsenic having a mass of 75, since counter-doping from arsenic residuesin Ge implantation can result. Such counter-doping in turn can renderimplanted microelectronic device structures deficient or even uselessfor their intended purpose. Thus, the usage of natural abundancegermanium dopant gas challenges the implanter's ability to resolveunwanted species and produce high current beams of the desired isotope,in instances in which arsenic is also implanted in other usage of thesame implanter, and can reduce the efficiency of cleaning operationsinvolving the ion source and beamline.

In addition to such cross-contamination with ⁷⁵As, the presence of ⁷⁴Gein ion implantation systems may produce cross-contamination withcorrosion byproducts of BF₃ or GeF₄ with stainless steel tubing thatdelivers the dopant gas to the arc chamber, e.g., FeF. Such issues ofcross-contamination are, however, absent in implanter systems in whicharsenic is not utilized as a dopant, and in which the dopant gasdelivery tube to arc chamber interface uses components of graphite,tungsten or other suitable materials that eliminate or minimize thegeneration of FeF. In such implanter systems, dopant gases containing⁷⁴Ge may be employed without the disadvantages of suchcross-contamination.

In ion implantation systems in which dopant gases containing ⁷⁴Ge can beutilized without adverse effect, the present disclosure, in one aspectthereof, contemplates the use of germanium-containing dopant gasenriched in ⁷⁴Ge beyond natural abundance, taking advantage of the factthat natural abundance concentration of ⁷⁴Ge is higher than other stablegermanium isotopes (⁷⁰Ge, ⁷²Ge and ⁷³Ge), as shown in Table I above.Such higher concentration of ⁷⁴Ge, relative to other stable isotopes innatural abundance isotopic compositions, enables enrichment levels abovenatural abundance to be more economically achieved for ⁷⁴Ge than forother germanium isotopes having lower natural abundance concentrationthat are enriched to a corresponding enrichment level. Alternatively,from the standpoint of capital equipment and process costs, the highernatural abundance concentration of ⁷⁴Ge can be advantageous to achievehigher enrichment content than is obtainable at the same cost for otherstable germanium isotopes (⁷⁰Ge, ⁷²Ge and ⁷³Ge).

To address the germanium implantation issues of arsenic contamination,in ion implantation systems in which arsenic doping is conducted, theless abundant mass 72 germanium isotope can be advantageously employed.However, the naturally occurring abundance of mass 72 germanium isotopein, for example, germanium tetrafluoride is 27.3%, as compared to 37.1%for mass 74 germanium isotope (see Table I, above). The use of naturalabundance germanium thus causes a reduction of available beam current,potential decrease in throughput, and an increase in implantation cost.

Accordingly, the use of isotopically enriched mass 72 germanium ingermanium tetrafluoride or germane, in accordance with the presentdisclosure, achieves significant benefit in increasing available beamcurrent, increasing throughput and decreasing implantation cost, inthose systems susceptible to cross-contamination due to the presence ofmass 74 germanium in the dopant composition. For example, the enrichmentof mass 72 germanium isotope, e.g., to a level greater than 27.3% ingermanium tetrafluoride or germane is beneficial in correspondinglyincreasing beam current which in turn is advantageous in yielding acorresponding increase in throughput in the ion implantation system.

Analogous benefits in increased beam current, throughput, and overallperformance, can be achieved with other isotopically enriched dopantcompositions, such as germanium tetrafluoride, or germane, isotopicallyenriched in ⁷⁰Ge.

The present disclosure thus broadly contemplates isotopically enricheddopant gases, and/or isotopically enriched co-species gases, in whichthe concentration of a beneficial isotope is increased in relation toits natural occurrence in such dopant and/or co-species gases, to suchextent as to improve the performance and lifetime of the ion source inthe ion implantation system, in relation to a corresponding system inwhich the dopant and/or co-species gases are not isotopically adjustedfrom natural abundance concentration levels. The term “isotopicallyenriched” is therefore to be understood as indicating an increasedconcentration, relative to natural abundance levels, of the particularisotopic species considered.

In various specific embodiments, the beneficial/desired isotope may beincreased, relative to natural abundance concentration, by the amount of5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 or more percent, above thenatural abundance concentration level of such isotope. In other specificembodiments, the beneficial/desired isotope may be enriched from thenatural abundance concentration level to a higher concentration level,such as 10, 20, 30, 40, 50, 60, 70, 80, 90, 99, 99.99 or more percent,depending on the specific isotopic species involved.

As used herein, the term “by” in reference to a percentage increase ofan isotope above the natural abundance concentration, such as in thephrase “increased, relative to natural abundance concentration, by theamount of . . . ” means that the percentage increase is based on thenatural abundance atomic percentage of the specified isotope in thespecified element or compound. Thus, for example, the phrase “increased,relative to natural abundance concentration, by the amount of 20percent, e.g., for ⁷⁰Ge in GeF₄, means that the 21.2% atomic percentnatural abundance for ⁷⁰Ge in GeF₄ is increased by 21.2%×1.20=25.4% of⁷⁰Ge in the isotopically enriched GeF₄ compound.

By contrast, the term “to” in reference to a percentage of an isotopeabove the natural abundance concentration, such as in the phrase“enriched from the natural abundance concentration level to a higherconcentration level of . . . ” means that the atomic percentconcentration in the isotopically enriched element or compound is thenumeric value specified. Thus, for example, the phrase “enriched fromthe natural abundance concentration level for ⁷⁰Ge in GeF₄ to a higherconcentration level of 40 percent, means that ⁷⁰Ge is present in anamount of 40 atomic % in the isotopically enriched GeF₄. If otherwisespecified than with reference to the terms “by” or “to” in phraseologysuch as the foregoing, reference to isotopic concentrations or levelswill be understood to refer to atomic percent concentration of theisotopically enriched element or compound having the specific identifiednumeric value.

In various embodiments, the beneficial isotope may be increased to amajor portion of the total isotopes in the composition, i.e., anisotopic concentration greater than 50% in the composition. For example,the mass 72 germanium isotope in germanium tetrafluoride and germane inspecific embodiments may be enriched to ≧52% and >27.3%, respectively.In other specific embodiments, the mass 70 germanium isotope ingermanium tetrafluoride or germane may be enriched to >21.2%.

Accordingly, germanium tetrafluoride enriched in mass 72 germaniumisotope may be advantageously enriched to levels of from at least 52% upto 100%, or to enrichment levels in other specified ranges, such as from55% to 100%, from 60% to 90%, from 75 to 95%, from 80 to 100% or otherpermutations of such ranges including one of such lower limits andanother of such upper limits, in which a desired level of increase inbeam current, enhancement in throughput and/or improved economiccharacter of the implantation operation is achieved. Germane enriched inmass 72 germanium isotope may be advantageously enriched to levels offrom above 27.3% up to 100%, or to enrichment levels in other specifiedranges, such as from 30% to 100%, from 35% to 85%, from 40% to 60%, from50% to 99%, from 75-95%, or other permutations of such ranges includingone of such lower limits and another of such upper limits, in which thedesired improvement in the aforementioned process characteristics ofbeam current, throughput and cost is achieved.

Correspondingly, germanium tetrafluoride enriched in mass 70 germaniumisotope may be advantageously enriched to levels of from greater than21.2% to 100% or to enrichment levels in other specified ranges, such asfrom 45% to 100%, from 50% to 99%, from 60% to 85%, from 75% to 98%, orother permutations of such ranges including one of such lower limits andanother of such upper limits, achieving the desired level of enhancementin beam current, throughput and cost. Corresponding use of germaneenriched in mass 70 germanium isotope may be employed, wherein theenrichment of ⁷⁰Ge is to levels of from greater than 21.2% to 100%, orto enrichment levels in other ranges, such as from 25% to 100%, from 30%to 99%, from 40% to 95%, from 50% to 90%, from 75% to 95%, from 80% to99%, or other permutations of such ranges including one of such lowerlimits and another of such upper limits, as may be appropriate to thespecific ion implantation operation and apparatus in which theisotopically enriched dopant gas is used.

The present disclosure therefore contemplates the achievement ofimproved lifetime and performance of an ion source in an ionimplantation system, by using dopant gases and/or supplemental gasesthat have been isotopically enriched to levels heretofore unknown in ionimplantation. The dopant gas may be isotopically enriched beyond naturalabundance, or the co-species gas when present may be isotopicallyenriched beyond natural abundance, or both the dopant gas and theco-species gas may be isotopically enriched beyond natural abundance.All combinations of isotopic enrichment beyond natural abundance,involving dopant gases, co-species gases, and diluent gases, arecontemplated as being within the scope of the present disclosure.

Examples of dopant gas mixtures that may be usefully employed in thepractice of the present disclosure to improve lifetime and performanceof an ion source include, without limitation, dopant gas compositionscomprising:

-   -   (1) isotopically enriched germanium tetrafluoride, in        combination with xenon and hydrogen as diluent gases;    -   (2) isotopically enriched germanium tetrafluoride, in        combination with germane as a co-species gas;    -   (3) isotopically enriched germanium tetrafluoride in combination        with isotopically enriched germane as a co-species gas;    -   (4) isotopically enriched boron trifluoride, in combination with        xenon and hydrogen as diluent gases;    -   (5) isotopically enriched boron trifluoride, in combination with        diborane as a diluent gas; or    -   (6) isotopically enriched boron trifluoride, in combination with        isotopically enriched diborane as a co-species gas.

In one specific embodiment, the dopant gas mixture includes atomic mass72 germanium having concentration of more than 55%, e.g., more than 60%,70%, 80%, or 90%, based on the total isotopic species of germanium thatare present, to provide a high level of beam current, improving boththroughput and source life.

In another specific embodiment, wherein the dopant gas mixture does notcomprise germanium tetrafluoride, the dopant gas mixture includes atomicmass 72 germanium having concentration of more than 25%, e.g., more than30%, 40%, 50%, 60%, 70%, 80%, or 90%, based on the total isotopicspecies of germanium that are present, to provide a high level of beamcurrent, improving both throughput and source life.

In still another specific embodiment, the dopant gas mixture includesatomic mass 70 germanium having concentration of more than 25%, e.g.,more than 30%, 40%, 50%, 60%, 70%, 80%, or 90%, based on the totalisotopic species of germanium that are present, to provide high levelsof beam current, and corresponding increases in throughput and sourcelife.

Dopant gas compositions in specific embodiments of the disclosure cancomprise a germanium-containing dopant gas and optionally a supplementalgas, wherein the supplemental gas includes at least one of a diluent gasand a co-species gas, and the dopant gas composition is isotopicallyenriched in at least one Ge isotopic species. Such compositions may inspecific embodiments include isotopically enriched germane, oralternatively isotopically enriched germanium tetrafluoride, oralternatively both isotopically enriched germane and germaniumtetrafluoride, or alternatively both germane and germanium tetrafluoridewherein only one of such germanium-containing components is isotopicallyenriched. In other embodiments, when germanium tetrafluoride is presentin an isotopically enriched form, the dopant gas composition may includegermanium tetrafluoride isotopically enriched in germanium of mass 70,72, 73, 74 or 76. Other embodiments may include germanium tetrafluorideisotopically enriched in germanium of mass 70, 73 or 74. Still otherembodiments may include germanium tetrafluoride isotopically enriched ingermanium of mass 70, 72 or 74. In some embodiments, when germanium ofmass 72 is present in germanium tetrafluoride, the isotopic enrichmentof such mass 72 isotope may be greater than 51.6%, e.g., greater than52%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, 99.9% or 99.99%in specific implementations, and isotopic enrichment from any of suchnumeric values of to 100% is contemplated within the broad scope of thepresent disclosure.

Dopant gas compositions in other embodiments may include agermanium-containing component, such as germane and/or germaniumtetrafluoride, in mixture with one or more of argon, helium, hydrogen,nitrogen, ammonia and xenon, wherein the germanium-containing componentoptionally is isotopically enriched, e.g., in germanium of mass 70, 72,73, 74 or 76. In one embodiment, the dopant gas composition includesgermanium tetrafluoride and ammonia, wherein the germanium tetrafluorideis isotopically enriched, e.g. in germanium of mass 70, 72, 73, 74 or76, and in another embodiment, wherein the germanium tetrafluoride isisotopically enriched in germanium of mass 72, the isotopic enrichmentof such mass 72 isotope may be greater than 51.6%, e.g., greater than52%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, 99.9% or 99.99%in specific implementations, and isotopic enrichment from any of suchnumeric values of to 100% is contemplated within the broad scope of thepresent disclosure.

In one illustrative embodiment, the disclosure relates to an ionimplantation process, wherein a dopant gas mixture comprising a dopantgas and optionally a supplemental gas is provided to an ion source forgeneration of ionic dopant species for implantation, wherein thesupplemental gas includes at least one of a diluent gas and a co-speciesgas, and wherein at least one of the dopant gas and, when present, thesupplemental gas, includes an isotopically enriched component.

In another embodiment, the disclosure relates to improving performanceand lifetime of an ion source arranged to generate ionic doping speciesfor ion implantation from a dopant gas, comprising using a dopant gasmixture comprising a dopant gas and optionally a supplemental gas,wherein the supplemental gas includes at least one of a diluent gas anda co-species gas, and wherein at least one of the dopant gas and, whenpresent, the supplemental gas, includes an isotopically enrichedcomponent.

A further embodiment of the invention relates to an ion implantationsystem, comprising a dopant gas source and an optional supplemental gassource, wherein each of the gas sources is arranged for dispensingrespective dopant gas and supplemental gas to a mixing locus in thesystem adapted for mixing of the dopant gas and supplemental gas to forma dopant gas mixture, and an ion source constituting the mixing locus orarranged to receive the dopant gas mixture from the mixing locus,wherein the supplemental gas includes at least one of a diluent gas anda co-species gas, and wherein at least one of the dopant gas and, whenpresent, the supplemental gas includes an isotopically enrichedcomponent. Thus, the dopant gas mixture can comprise a dopant gas and asupplemental gas, wherein both the dopant gas and the supplemental gasinclude an isotopically enriched component (e.g., beneficial/desiredisotope), or the dopant gas and the supplemental gas can both beisotopically enriched in different isotopic components.

Additional embodiments of the disclosure relate to use of isotopic mass70 germanium dopant gas and/or co-species gas usage in ion implantation,wherein the dopant gas and/or co-species gas is isotopically enriched inatomic mass 70 germanium beyond natural abundance level, e.g., a levelof at least 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%,90%, 95%, 99%, 99.5%, 99.99%, or other level appropriate to the specificion implantation application employed.

An additional embodiment of the disclosure relates to utilization of adopant gas reagent including a dopant gas and a co-species, wherein thegas may be of a composition as described herein, including isotopicallyenriched dopant gas and/or co-species gas components.

In a further embodiment, the dopant reagent including the dopant gas andco-species gas is arranged in the ion implantation system to be flowedto the ion source for supply thereof, wherein the dopant gas and theco-species gas are in mixture with one another.

In a further embodiment, the dopant gas and the co-species gas aresequentially flowed to the ion source for ionization therein. Suchsequential operation may be conducted in any suitable manner, utilizingequal time-based flows of the respective dopant gas and co-species gas,or alternatively, the respective time-based flows may be different inrespect of each other, or otherwise modulated to provide a dopedsubstrate of desired character.

The substrate that is ion implanted with ionic species in accordancewith the present disclosure, may be of any suitable type.

The substrate may be silicon, silicon carbide, gallium nitride, or anyother suitable substrate composition. Substrates may includemicroelectronic device substrates, i.e., substrates utilized to preparemicroelectronic structures for manufacturing of microelectronic devicesor device precursor components.

In other embodiments, the substrate may be implanted for manufacturer ofproducts such as displays and solar panels. It will be recognized thatthe disclosure is applicable to ion implantation applications of anysuitable character.

In one embodiment, the present disclosure relates to a dopantcomposition supply apparatus including a vessel having an interiorvolume and a dopant composition in the interior volume, wherein thedopant composition may be of any suitable type as described. Such dopantcomposition supply apparatus may be arranged for coupling with an ionsource, e.g., by means of suitable flow circuitry containing appropriateinstrumentation and control components for effecting appropriate flow ofdopant composition to the ion source.

Referring now to the drawings, FIG. 1 is a schematic representation ofan ion implant process system according to one aspect of the disclosure.

The ion implant process system 300 includes a storage and dispensingvessel 302 containing having an interior volume holding a dopant gasthat is supplied for ion implantation doping of a substrate 328 in theillustrated ion implant chamber 301. The storage and dispensing vesselmay be of a type containing a sorbent medium on which the dopant gas isphysically adsorbed for storage of the gas, with the gas being desorbedfrom the sorbent medium, under dispensing conditions, for discharge fromthe vessel. The sorbent medium may be a solid-phase carbon adsorbentmaterial. Sorbent-based vessels of such type are commercially availablefrom ATMI, Inc. (Danbury, Conn., USA) under the trademarks SDS and SAGE.Alternatively, the vessel may be of an internally pressure-regulatedtype, containing one or more pressure regulators in the interior volumeof the vessel. Such pressure-regulated vessels are commerciallyavailable from ATMI, Inc. (Danbury, Conn., USA) under the trademark VAC.As a still further alternative, the vessel may contain the dopant sourcematerial in a solid form that is volatilized, e.g., by heating of thevessel and/or its contents, to generate the dopant gas as a vaporizationor sublimation product. Solid delivery vessels of such type arecommercially available from ATMI, Inc. (Danbury, Conn., USA) under thetrademark ProEvap.

In FIG. 1, the storage and dispensing vessel 302 comprises a cylindricalvessel wall 304 enclosing an interior volume holding the dopant gas inan adsorbed state, a free gas state, or a liquefied gas state.

The storage and dispensing vessel 302 includes a valve head 308 coupledin gas flow communication via a dispensing line 372 with a mixingchamber 360 (which is optional), joined in turn to discharge line 312. Apressure sensor 310 may be disposed in the line 312, together with amass flow controller 314; other optional monitoring and sensingcomponents may be coupled with the line, and interfaced with controlmeans such as actuators, feedback and computer control systems, cycletimers, etc.

The mixing chamber 360 also if used may be joined in flow communicationwith gas feed line 370, to which are coupled supplemental gas supplyvessels 362 and 364, each of which may be of a same or different typerelative to one another, and which may be of a same or different type inrelation to vessel 302 above described. Vessel 362 may for examplecontain a diluent gas, and vessel 364 may for example contain aco-species gas, arranged so that dopant gas mixtures can be prepared,containing the dopant gas in combination with the diluent gas and/or theco-species gas.

Supplemental vessel 362 is formed with a main container portion to whichis secured a valve head 380 that is in turn coupled with supplementalvessel feed line 366. In like manner, supplemental vessel 364 is formedwith a main container portion to which is secured valve head 382. Valvehead 382 is coupled to supplemental vessel feed line 368. Feed lines 366and 368 by such arrangement deliver diluent and/or co-species gas(es) tothe mixing chamber 360, to provide a dopant gas mixture containingdiluent and/or co-species gas(es), for passage to the ion source of theimplanter. For such purpose, the supplemental vessel feed lines 366 and368, and dispensing line 372 may be equipped with suitable valves,controllers and/or sensors for manually or automatically controlling theflow or other characteristics of the materials dispensed from thevessels and such valves, controllers and/or sensors can be coupled withor connected to the corresponding feed/dispensing lines in any suitablemanner.

Such valves may in turn be coupled with valve actuators operativelylinked to a central processor unit (CPU). The CPU may be coupled insignal communication relationship with the aforementioned controllersand/or sensors, and programmably arranged to control the rates,conditions and amounts of fluids dispensed from each of the vessels inrelation to each other, so that the dopant gas mixture flowed from themixing chamber 360 in line 312 has a desired composition, temperature,pressure and flow rate for carrying out the ion implantation operation.

In the illustrated system 300, the ion implant chamber 301 contains anion source 316 receiving the dispensed dopant gas mixture from line 312and generates an ion beam 305. The ion beam 305 passes through the massanalyzer unit 322 which selects the ions needed and rejects thenon-selected ions.

The selected ions pass through the acceleration electrode array 324 andthen the deflection electrodes 326. The resulting focused ion beam isimpinged on the substrate element 328 disposed on the rotatable holder330 mounted on spindle 332. The ion beam of dopant ions is used to dopethe substrate as desired to form a doped structure.

The respective sections of the ion implant chamber 301 are exhaustedthrough lines 318, 340 and 344 by means of pumps 320, 342 and 346,respectively.

FIG. 2. is a schematic representation of an ion implant process systemaccording to another aspect of the disclosure. The FIG. 2 system isnumbered correspondingly with respect to the same components andfeatures of FIG. 1 but the FIG. 2 system utilizes the respective dopantgas and supplemental gas vessels in a flow circuitry arrangement whereineach of the vessels 304, 362 and 364 has a separate mass flow controller314, 400 and 402, respectively, in its dispensing line. By thisarrangement, the flow of gas from each of the respective vessels ismodulated by a dedicated mass flow controller in the associateddispensing line, to achieve selected flow rates or flow rate ratios ofthe respective gases in operation. The respective mass flow controllersmay be operatively linked with a central processor unit (CPU) by whichthe respective mass flow controllers can be adjusted in operation asnecessary or desirable to achieve optimal operation of the system.

In a further aspect of the present disclosure, the dopant gas may besupplied in the first instance in a mixture containing one or moresupplemental gas(es), i.e., a diluent and/or co-species gas, in whichthe mixture of dopant gas and supplemental gas is contained in a singlesupply vessel, from which the gas mixture can be dispensed and flowed tothe ion source of the ion implantation system. For example, in the FIG.1 system, the vessel 302 can constitute a single gas supply vessel (withsupplemental vessels 362 and 364 being absent) containing the dopant gasand supplemental gas mixture.

Such approach may be utilized to provide germane as a dopant gas in amixture comprising hydrogen, an inert gas or other diluent gas, as aco-packaged mixture that can be provided from a single supply vessel.This is a safer packaging technique as compared to high pressure 100%germane, and enables germane to be used as an alternative to germaniumtetrafluoride, since germanium tetrafluoride can in some ion implantapplications cause problems with respect to source life and turbo pumplife that are avoided by the use of germane.

As an illustrative example of germane gas mixtures that can beadvantageously used in the broad practice of the present disclosure, asprovided in a single supply vessel, the germane-containing gascomposition can comprise from 5 to 35 volume % germane, based on thetotal volume of the composition, or other suitable concentration ofgermane, with the balance being one or more of hydrogen, argon,nitrogen, and helium, wherein the germane is either natural abundancegermane, or germane that is isotopically enriched in ⁷⁰Ge or ⁷²Ge orother germanium isotope, or wherein the dopant gas mixture containinggermane is optionally otherwise isotopically enriched in at least one Geisotopic species.

In another aspect, the present disclosure relates to use of ammonia as aco-flow gas with germanium tetrafluoride, to increase source life in ionimplantation systems in which germanium tetrafluoride is used as adopant gas, and wherein the germanium tetrafluoride optionally may beisotopically enriched in at least one Ge isotopic species. By usingammonia as a supplemental gas in mixture with germanium tetrafluoridewhen implanting germanium, the nitrogen and hydrogen constituents ofammonia (NH₃) will effectively scavenge fluorine from the germaniumtetrafluoride. As a result of such fluorine scavenging, the GeF₄/NH₃mixture will at least partially inhibit the halogen cycle within the ionsource that results in poor source life due to tungsten whiskers growingon the arc slit and/or tungsten depositing on the cathode and/oranticathode.

Such usage of ammonia as a co-flow gas with GeF₄ can be effected in anyof a variety of arrangements. In one embodiment, separate gas supplyvessels for ammonia and germanium tetrafluoride are employed, and thegases from the respective gas supply vessels are co-flowed to the ionsource. The co-flowed gases may be mixed prior to passage through a massflow controller, or mixed between a mass flow controller and the ionsource, or mixed within the ion source.

Alternatively, a single supply vessel containing a mixture of ammoniaand germanium tetrafluoride, in any suitable relative proportions, canbe provided.

As a further alternative, xenon can be provided as a supplemental gas ina separate supply vessel. After being dispensed from the supply vessel,the xenon can be mixed with ammonia and/or germanium tetrafluoride.Xenon can also be provided as a supplemental gas in a gas vesselcontaining xenon mixed with ammonia and/or germanium tetrafluoride. Thepresence of xenon in the gas introduced to the ion source improvessource life by the sputtering effect of the xenon on the cathode, toremove any excess tungsten that deposits on such cathode.

The disclosure in yet another aspect relates to an improved ionimplantation process that comprises, consists essentially of, orconsists of flowing one or more isotopically enriched dopant material,such as for example germane or germanium tetrafluoride, into an ionizingchamber to generate ionic dopant species, extracting the ionic dopantspecies from the ionizing chamber, selecting a predetermined ionicdopant species and implanting the selected/desired ionic dopant speciesinto a microelectronic or semiconductor substrate.

In various embodiments, the beneficial/desired isotope may be increased,relative to natural abundance concentration, by an amount of 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60 or more percent above the naturalabundance concentration level of such isotope, or the beneficial/desiredisotope may be enriched from the natural abundance concentration levelto a higher concentration level such as 10, 20, 30, 40, 50, 60, 70, 80,90 or more percent, depending on the natural abundance level of thespecific isotopic species involved. The enrichment of a desiredgermanium isotope is provided to increase the abundance or concentrationof such isotope and correspondingly increase the quantity of the isotopein the ion beam. This in turn yields a corresponding advantage inthroughput as compared with systems and/or processes that utilize agermanium source containing a lower concentration/amount of thesame/desired germanium isotope.

In one preferred embodiment, a germanium tetrafluoride gas containing≧52% atomic mass 72 germanium isotope, a germane gas containing >27.3%atomic mass 72 germanium isotope, or a mixture of both gases is used asthe dopant material. In another preferred embodiment, a germaniumtetrafluoride gas containing ≧21.2% atomic mass 70 germanium isotope, agermane gas containing >21.2% atomic mass 70 germanium isotope, or amixture of both gases is used as the dopant material.

In dopant gas compositions comprising a germanium-containing dopant gasand optionally a supplemental gas, wherein the supplemental gas includesat least one of the diluent gas and a co-species gas, and the dopant gascomposition is isotopically enriched in at least one Ge isotopicspecies, the composition may comprise at least one of germane andgermanium tetrafluoride, in which either or both of such components isisotopically enriched, e.g., in germanium of mass 70, 72, 73, 74 or 76,or alternatively in germanium of mass 70, 72 or 74. In such composition,when germanium tetrafluoride is present and is isotopically enriched ingermanium of mass 72, the isotopic enrichment level may be greater than51.6%. The dopant gas composition may include a supplemental gas of anysuitable character.

Dopant gas compositions are contemplated that comprise agermanium-containing component and one or more of argon, helium,hydrogen, nitrogen, ammonia and xenon, wherein the germanium-containingcomponent optionally is isotopically enriched. The germanium-containingcomponent in specific embodiments may comprise germane and/or germaniumtetrafluoride. The dopant gas composition in a specific embodiment maycomprise ammonia. In other embodiments, the composition may for exampleconsist of germanium tetrafluoride and ammonia, in which the germaniumtetrafluoride is isotopically enriched. Alternatively, the compositionmay comprise isotopically enriched germanium tetrafluoride and at leastone of ammonia and xenon.

A further aspect of the disclosure relates to sequential flow of dopantmaterials, in which cathode bias power is monitored during operation ofthe ion source and the monitored cathode biased source power is utilizedin a feedback control process for controlling/selecting/alternatingbetween respective ones of the dopant compounds delivered to the ionsource, in order to extend the operating lifetime of the ion source orits components, e.g., by maintaining a predetermined cathode bias powerin the operation of the ion source. Such method can be utilized torepair or remediate the cathode of the ion source, i.e., to effectregrowth or etching of the cathode, as required to maintain or otherwiseachieve a predetermined cathode bias power in the operation of the ionsource.

The ion source may be of any suitable type in such monitored andcontrolled process, e.g., an indirect hot cathode (IHC) ion source.Cathode bias power in such method is advantageously used as a feedbackmechanism to control sequential flow of different dopant compounds toextend the operating lifetime of the ion source/cathode.

The different dopant compounds may be, and preferably are, dopantcompounds for the same dopant species, e.g., germanium tetrafluoride andgermane as dopant compounds for the dopant species germanium. Suchdifferent dopant source compounds may include at least one that isisotopically enriched, as variously described herein.

This method of operating an ion implantation system including a cathodein an arc chamber of an ion source, to maintain operating efficiency ofthe ion source, in one embodiment includes contacting the cathode withsequentially supplied dopant compositions, while measuring cathode biaspower, and in response to the measured cathode bias power, modulating atleast one of said sequentially supplied dopant compositions, to extendoperating lifetime of the ion source, cathode and/or one or more othercomponents of the ion source.

The term “modulating” in reference to the sequentially supplied dopantcompositions, means that the sequence, duration, process conditions, ordopant composition selection for at least one of the sequentiallysupplied dopant compositions is controlled, i.e., selectively varied, inresponse to the measured cathode bias power. Thus, the supply periodsfor each of the dopant compositions may be varied in relation to oneanother, to maintain a set point cathode bias power value, or one dopantcomposition may be supplied at higher voltage conditions than another,or the feedback monitoring and control system may be arranged tootherwise control/select/alternate between the respective dopantcompositions.

In another embodiment, the method may be utilized to flow concurrentlyor sequentially a cleaning agent or a deposition agent through the ionsource, in relation to one or more dopant compositions, wherein thecathode bias power or other power utilization variable of the ion sourceis utilized to effect etching of the cathode to remove depositstherefrom, e.g., if the monitored power usage increases above an initialor other predetermined or setpoint value or level, by flowing and etchcleaning agent through the ion source, and/or wherein the cathode biaspower or other power utilization variable of the ion source is utilizedto effect regrowth of cathode material by flow of a deposition agenttherefore through the ion source, if the monitored power usage decreasesbelow an initial or other predetermined or setpoint value.

It will therefore be appreciated that the compositions, processes,methods, apparatus and systems of the disclosure are susceptible toimplementation and application in a wide variety of manners, to providecorresponding improvements in performance and lifetime of an ion sourcein an ion implantation system.

While the disclosure has been has been set out herein in reference tospecific aspects, features and illustrative embodiments, it will beappreciated that the utility of the disclosure is not thus limited, butrather extends to and encompasses numerous other variations,modifications and alternative embodiments, as will suggest themselves tothose of ordinary skill in the field of the present invention, based onthe description herein. Correspondingly, the invention as hereinafterclaimed is intended to be broadly construed and interpreted, asincluding all such variations, modifications and alternativeembodiments, within its spirit and scope.

1. An ion implantation process, comprising: flowing a dopant compositionto an ion source; generating ionic dopant species from the dopantcomposition at the ion source; and implanting the ionic dopant speciesin a substrate, wherein the dopant composition is selected from thegroup consisting of the following dopant compositions (i) and (ii): (i)dopant compositions comprising one or more germanium compoundsisotopically enriched to above natural abundance level of at least onegermanium isotope of mass 70, 72, 73, 74 or 76, wherein the isotopicallyenriched level of said at least one germanium isotope is greater than21.2% for mass 70 germanium isotope, greater than 27.3% for mass 72germanium isotope, greater than 7.9% for mass 73 germanium isotope,greater than 37.1% for mass 74 germanium isotope, and greater than 7.4%for mass 76 germanium isotope; and (ii) dopant compositions comprising adopant gas and a supplemental gas, wherein the supplemental gas includesat least one of a diluent gas and a co-species gas, and wherein at leastone of the dopant gas and, when present, a co-species gas, isisotopically enriched; with the proviso that when the dopant compositionof dopant composition (i) or isotopically enriched dopant gas orco-species gas of dopant composition (ii) consists of germaniumtetrafluoride isotopically enriched in mass 72 germanium isotope, saidisotopically enriched level is greater than 51.6% for the mass 72germanium isotope.
 2. The process of claim 1, wherein the dopantcomposition is selected from the group consisting of dopant compositions(i).
 3. The process of claim 2, wherein the one or more isotopicallyenriched germanium compounds comprise germane.
 4. The process of claim2, wherein the one or more isotopically enriched germanium compoundscomprise germanium tetrafluoride.
 5. The process of claim 2, wherein theone or more isotopically enriched germanium compounds comprise germaneand germanium tetrafluoride.
 6. The process of claim 1, wherein thedopant composition is selected from the group consisting of dopantcompositions (ii).
 7. The process of claim 6, wherein the dopantcomposition comprises one or more germanium compounds isotopicallyenriched above natural abundance level of at least one germanium isotopeof mass 70, 72, 73, 74 or
 76. 8. The process of claim 7, wherein thedopant composition comprises isotopically enriched germane.
 9. Theprocess of claim 7, wherein the dopant composition comprisesisotopically enriched germanium tetrafluoride.
 10. The process of claim7, wherein the dopant composition comprises isotopically enrichedgermane and isotopically enriched germanium tetrafluoride.
 11. Theprocess of claim 6, wherein said supplemental gas includes one or morediluent gas selected from the group consisting of argon, hydrogen,nitrogen, helium, ammonia, fluorine and xenon.
 12. The process of claim6, wherein said supplemental gas comprises one or more co-species gasselected from the group consisting of germanium tetrafluoride, germane,boron trifluoride, diborane, silicon tetrafluoride and silane.
 13. Theprocess of claim 6, wherein said dopant gas is selected from the groupconsisting of germanium tetrafluoride, germane, boron trifluoride,diborane, silicon tetrafluoride and silane.
 14. The process of claim 6,wherein the dopant composition comprises a dopant gas formulationselected from the group consisting of: (i) xenon, hydrogen, andisotopically enriched germanium tetrafluoride; (ii) germane andisotopically enriched germanium tetrafluoride; (iii) isotopicallyenriched germanium tetrafluoride and isotopically enriched germane; (iv)xenon, hydrogen, and isotopically enriched boron trifluoride; (v)diborane and isotopically enriched boron trifluoride; and (vi)isotopically enriched boron trifluoride and isotopically enricheddiborane.
 15. A dopant composition comprising a dopant gas and asupplemental gas, wherein the supplemental gas includes at least one ofa diluent gas and a co-species gas, and wherein at least one of thedopant gas and, when present, a co-species gas, is isotopicallyenriched, with the proviso that when the isotopically enriched dopantgas or co-species gas of the dopant composition consists of germaniumtetrafluoride isotopically enriched in mass 72 germanium isotope, saidisotopically enriched level is greater than 51.6% for the mass 72germanium isotope.
 16. The composition of claim 15, comprising one ormore germanium compounds isotopically enriched above natural abundancelevel of at least one germanium isotope of mass 70, 72, 73, 74 or 76.17. The composition of claim 16, comprising at least one of isotopicallyenriched germane and germanium tetrafluoride.
 18. The composition ofclaim 15, wherein said dopant gas is selected from the group consistingof germanium tetrafluoride, germane, boron trifluoride, diborane,silicon tetrafluoride and silane.
 19. The composition of claim 15,wherein the supplemental gas comprises at least one gas selected fromthe group of argon, hydrogen, nitrogen, helium, ammonia, fluorine,xenon, germanium tetrafluoride, germane, boron trifluoride, diborane,silicon tetrafluoride, and silane.
 20. The composition of claim 15,wherein the dopant composition comprises a composition selected from thegroup consisting of: (i) xenon, hydrogen, and isotopically enrichedgermanium tetrafluoride; (ii) germane and isotopically enrichedgermanium tetrafluoride; (iii) isotopically enriched germaniumtetrafluoride and isotopically enriched germane; (iv) xenon, hydrogen,and isotopically enriched boron trifluoride; (v) diborane andisotopically enriched boron trifluoride; and (vi) isotopically enrichedboron trifluoride and isotopically enriched diborane.